Download HijackThis from here
http://www.merijn.org/files/hijackthis.zip
Go here for an excellent Tutorial on using HijackThis (HJT):
http://www.thinkdigit.com/forum/viewtopic.php?t=15729
Run HJT, save the log file and post it back here so we can fix your problem once and for all.
As for the 'smss.exe' problem, click Start>Run and type in regedit. In the Registry Editor that opens, on the left, navigate to :
HKEY_CURRENT_USER\Software\Microsoft\Windows\Curre ntVersion\Run
and
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Curr entVersion\Run
and see on the right hand side if there is any reference to the smss.exe file. If there is, right click that key alone and delete it. Check the screenshot below for an example, if you get confused.
Do this and you wont see the 'smss.exe' file-not-found error at startup. Also, remember to post your HJT log file here.